Automatic toaster



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Sept 17, 1957 L. J. KOCI AUTOMATIC TOASTER Original Filed Jan. 30, 1948ll Sheets-Sheet l0 INVENTOR; Z M01 41 fZJcz Sept 17, 1957 L. J. KOCIAUTOMATIC TOASTER 11 Sheets-Sheet 11 Original Filed Jan. 30, 1948JNVENTGR. Jzzaazk Qf 127001;

United States Patent AUTOMATIC TOASTER Ludvik J. Koci, Hinsdale, llL,assiguor to Sunbeam Corporation, Chicago, lil., a corporation ofIllinois Original application January 39, 1948, Serial No. 5,247, nowPatent No. 2,667,828, dated February 2, 1954. Divided and thisapplication June 22, 1953, Serial No. 363,275

4 Claims. (Cl. 913-331) The present invention relates to cooking devicesfor heat treating food, and more particularly relates to automatictoasters. Specifically, the present invention is a division of copendingapplication, Serial No. 5,247, filed January 30, 1948, now Patent No.2,667,828.

Automatic toasters have been extensively used in recent years. Suchautomatic toasters have generally comprised an arrangement whereby toastis inserted into the toaster and manually moved to the toastingposition, whereupon the bread carriage is releasably latched in suchtoasting position. In moving the bread carriage to the toastingposition, an energy storage means is conventional- 13 stressed.Automatic means are provided to release the carriage when the toastingoperation is completed whereby the energy storage means is released tocause so-called pop-up action of the toast and bread carriage so thatthe toast may readily be removed therefrom. It would be desirable toprovide a more fully automatic toaster, that is one which would gothrough its entire toasting operation in response to only the insertionof the bread slice. Such a toaster would include means for automaticallymoving the bread slice to the toasting position, whereupon the toastingoperation could be performed thereon and at the end of the toastinginterval the bread slice would be moved to a position for ready removalthereof from the toaster without any manual operation other than theinsertion of the bread slice into the opening therefor defined in thetoaster. One such more fully automatic toaster is disclosed and claimedin United States Letters Patent No. 2,347,385, Wright and Jepson,granted April 25, 1944, and assigned to the same assignee as the presentapplication. The present invention is an improvement on the arrangementdisclosed and claimed in the above-mentioned Wright and Jepson patentinsofar as more fully automatic operation of an automatic toaster isconcerned.

Accordingly, it is an object of the present invention to provide a newand improved automatic toaster.

A further object of the present invention is to provide a more fullyautomatic toaster of a new and improved type in which the manual placingof a slice of bread into the toaster starts the mechanism through acycle of operations during which the bread is toasted and subsequentlymade available for manual removal from the toaster and in which allthese operations are automatically performed in response to merelyplacing the bread in the toaster and removing it therefrom.

A still further object of the present invention is to provide new andimproved heating elements for an automatic toaster which permit uniformtoasting of the bread surface regardless of the age or extent of use ofthe toaster and which furthermore are especially adapted for a controlarrangement in which a large amount of the heat radiated from a largearea of the bread surface being toasted is employed to control thetoasting interval in a manner so that said control arrangement is notaffected by direct radiation from the toasting elements, which permit ofready shielding in this respect.

Further objects and advantages of the present invenice 2 tion willbecome apparent as the following description proceeds, and the featuresof novelty which characterize the invention will be pointed out withparticularity in the claims annexed to and forming a part of thisspecification.

For a better understanding of the present invention reference may be hadto the accompanying drawings in which:

Fig. 1 is a perspective view of an automatic toaster embodying thepresent invention;

Fig. 2 is a partial end view of the toaster of Fig. 1 for the purpose ofbetter showing the only manual controls provided thereon;

Fig. 3 is a perspective view of the toaster of the present inventionwith the shell and base thereof removed and with the mechanism shown inthe toast receiving position;

Fig. 4 is a view similar to Fig. 3 but showing the toaster with thebread supporting carriage moved to the toasting position;

Fig. 5 is a side elevational view partly in section of the toastermechanism of the present invention with the shell and base indicated bydashed lines, with the bread supporting carriage indicated in the toastreceiving position, and with the control switch in the open position;

Fig. 6 is a view similar to Fig 5 with the mechanism of the presentinvention shown in the position it assumes immediately after a slice ofbread has been inserted into the toaster for toasting purposes to closethe control switch but before the bread has moved into the toastingposition;

Fig. 7 is a top plan view with substantially one-half thereof shown insection taken on line 7-7 of Fig. 5;

Fig. 8 is a sectional view taken on line 88 of Fig. 5 showing thecentral heating element and the thermomotive device employed in theautomatic toaster of the present invention;

Fig. 9 is a sectional view through the base of the automatic toastershowing the bottom cover assembly and the method of supporting the crumbtrays;

Fig. 10 is a top view of the bottom cover assembly shown in Fig. 9 ofthe drawings;

Fig. 11 is an end view of the thermostat assembly of the automatictoaster of the present invention with the switch in the closed position;

Fig. 12 is a sectional view Fig. 11;

Fig. 13 is a side elevational view of the assembly of Fig. 11 looking inthe direction of the arrows 1313 of Fig. 11;

Fig. 14 is a rear elevational Fig. 11 looking substantially arrows 14-14of Fig. 13;

Fig. 15 is a front elevational view of the cord and heating element ofthe automatic toaster of the present invention;

F Fig.516 is a side View of the end heating element of Fig. 17 is anelevational view similar to Fig. 15 of the thermostat end heatingelement of the automatic toaster of the present invention;

r Fig. 18 is a side view of the end heating element of Fig. 19 is aschematic circuit diagram of the electrical circuit and controlarrangement of the automatic toaster of the present invention;

Fig. 20 is a somewhat schematic view of the bread carriage, trip leverand associated apparatus of the automatic toaster of the presentinvention with the parts in the positions assumed after the toastingoperation has been completed and the toast moved to the nontoastingposition, but before the toast has been removed from the toastingchamber;

taken on line 12-12 of view of the assembly of in the direction of the tI v 2,806,422

Fig. 21 is a curve diagram to aid in understanding the operation of theautomatic toaster of the present invention; and

Figs. 22, 23 and 24- are heat radiation patterns to aid in understandingthe operation of certain of the heating units of the present invention.

As was mentioned above, the automatic toaster of the present inventionembodies the bread surface temperature radiation control arrangementdisclosed and broadly claimed in the above-mentioned copending Kociapplica tion.

Frame and shell structure Referring now to the drawings, the automatictoaster generally designated by the reference numeral 25 in Fig. l ofthe drawings comprises an outer casing generally designated at 26comprised of a pair of end shells 27 and 28 and a U-shaped central shellmember 29 cooperating with the end shells 26 to provide an outer housingor casing for the toaster. A suitable base 36 is also provided,preferably formed of a suitable molded insulating material, which baseincludes integrally formed handle portions 31 and 32 at either endthereof and suitable feet 33 at the bottom thereof. It will beunderstood that the particular configuration of the outer shell 26 andthe base is immaterial as far as the present invention is concerned,although these elements will be designed to produce the desired estheticeffect since they are the exposed portions by means of which the toastermay be given a very pleasing appearance.

The shell or outer casing 26 includes spaced parallel slots 34 and 35 atthe top for the insertion of slices of bread to be controlled in amanner to be described hereinafter by certain features of the presentinvention. It will be apparent that the illustrated embodiment is a conventional two slice toaster. Actually, it might equally well be a singleslice toaster or a toaster for more than two slices. Visible through thetoasting slots 34 and 35 are a plurality of vertically disposed guidewires 36 preferably formed of stainless steel and suitably supported inthe toaster frame to be described hereinafter. These guide wires definethe toasting chambers and guide the toast in its vertical movementwithin the toasting slots 34 and 35 without substantially interferingwith radiation between the heating elements and the bread to be toasted,as is brought out by the following description.

In accordance with the present invention, the automatic toaster 25requires substantially no manual control other than the insertion of thebread to be toasted in the slots 34 and 35 and the removal thereof uponcompletion of the toasting operation. For the purpose of controlling therelative lightness or darkness of the toast produced, there is provideda manually actuable color control lever 38 movable through a substantialare within a slot 3% defined between an upwardly extending arcuatemember 49 and the end shell 27. Preferably the arcuate member 40 is anintegral molded extension of the base 3-9. The control lever 38 ispivotal about an axis extending through an opening 41 defined in thebase 38 adjacent the handle 31 (See Fig. 9 of the drawings). The opening41 is adapted to receive a manually actuable cutout plunger 42 wherebythe toasting operation may be terminated at will. This plunger 42, whichis reciprocally movable, is described in greater detail hereinafter withrespect to its relation to the other mechanism of the automatic toaster25. The lever 38 and the plunger 42 are the only manual controlsemployed or required in the automatic toaster 25 embodying thepresent'invention.

Referring now to Figs. 3, 4-, 5, 6, 7 and'S of the drawings, Where insome cases the shell 26 and the base are indicated by dashed lines, itis noted that within the outer shell or housing 26 there is disposed aninner frame generally designated at 45. This inner frame comprises apair of side frame plates 46 and 4'7, a subbase plate 50, a pair of endtop frame plates 51 and 52, and a center top frame plate 53. For thepurpose of increasing the rigidity thereof, the side frame plates may beprovided with a plurality of vertical ribs 455 and a substantial portionof each end of the side frame plates 46 and 47 is bent at an angle,these angular extensions being designated as 46a and 47a for the plates46 and 4-7 respectively. For the purpose of providing additionalstrength, the subbase 5th is provided with a depending peripheral flange5th: around a substantial portion thereof. The top frame plates 51, 52and 553 are indicated as having a generally U-shaped configuration toprovide additional rigidity with the open end of each U extendingupwardly. The end top frame plates 51 and 52 are each spaced from thecenter top frame plate to define a pair of spaces or slots in alignmentwith the bread receiving slots 34 and 35 defined in the shell 26. Thearms of the t.lshaped end top frame plates 51 and 52. adjacent therespective ends of the toaster are divided to form two verticalextensions 49 for supporting the respective end shells 2'7 and 28. Thetop end plates 51 and 52 are preferably identical to decrease the numberoi. ditferent parts, and each is provided with a horizontal extension 4%between the vertical extensions 4-5. The horizontal extension 49a of theend top frame plate 51 contains a screw receiving opening to perform aholding operation described hereinafter. The frame plates or members 46,47, 50, 51, 52 and 53 may be joined to form the frame by means of anysuitable fastening means such as bolts, screws, welding or the like. Itmay be noted in Figs. 5 and 6 of the drawings that the top frame plates51, 52 and 53 are provided with downwardly extending tabs 51a, 52a and53a, respectively, so as to be fastened to side frame plates 46 and 47by means of self-tapping screws 5%. Similarly, the subbase 5G isprovided with punched out upwardly extending tabs 5 b which are fastenedto the angular extensions 46a and 47a the side frame plates 46 and 4'7,respectively, by self-tapping screws 54.

The subbase is provided with suitable flanged openings 55 and 56 definedtherein, disposed in alignment with the bread receiving slots 34 and 35,respectively, as well as the spaces defined between the end top frameplates 51 and 52, and the center top frame plate 53, whereby any crumbsfrom the bread being toasted may fall through the subbase 50 intosuitable crumb receiving trays to be described hereinafter and clearlyshown in Figs. 9 and 10 of the drawings. The subbase 50 is fur therprovided with a plurality of additional openings for accommodatingcertain elements of the toaster. For example, openings 57 defined in thesubbase 50 (see Figs. 3, 4, 7 and 8) are provided to receive extensionsof a lifter lever depressor bar 58 described in detail hereinafter. Theside frame plates 46 and 47 are also each provided with a notched outportion 59 along the bottom edge thereof cooperating with the openings57 in the subbase 50 so as not to interfere with movement of the lifterlever depressor bar 58. Openings 50c and 50d for receiving andsupporting extensions of the heating element assemblies are alsoprovided in the subbase 50 and, as shown in Figs. 8 and 9 of thedrawings, an opening 61 is provided between the flanged openings 55 and56 for permitting connection between a thermomotive device generallydesignated at 60, for causing movement of the Itgoast to and from thetoasting position, and the depressor The vertical guide wires 36referred to above extend through openings 62 in the U-shaped top frameplates 51, 52 and 53 with the upper ends thereof suitably fastenedthereto as by'welding indicated at 63 in Fig. 7 of the drawings. Thelower ends of the guide wires are provided with hooked portions forengaging spaced notches 64 cut into depending flanges 65 and 66surrounding the openings 55 and 56, respectively. The notches 64 alongone side of depending flange 66 are clearly shown in Fig. 8 of thedrawings. The vertical guide wires 36 actually define the toastingchambers designated as 67 and 68 which are accessible through the slots34 and 35, respectively, in the shell 26 between the center top frameplate 53 and the end top frame plates 51 and 52, respectively.

Solely for the purposes of simplifying the ensuing descr-iption, the endof the automatic toaster adjacent the end top frame plate 51 isdesignated as the thermostat end, while the end adjacent the end topframe plate 52 is designated as the cord end. The reason for thesedesignations will be obvious from the following description. It shouldbe understood that the thermostat or other control device employed andpower cord could be disposed at either end of the toaster or at the sameend for that matter.

Bread carriage mechanism It will be understood that in any automatictoaster means must be provided not only for supporting the material tobe toasted, usually bread slices, in the toasting position, but also formoving the material to be toasted from a toast receiving position to atoasting position, and

upon the completion of the toasting operation back to the toastreceiving position so that the toast may readily be removed. T 0 thisend, there are disposed in the toasting chambers 67 and 68 (Fig. 7 ofthe drawings) a pair of horizontally disposed vertically movable breadracks or supports 69 land 70, the bread rack 69 being disposed in thetoasting chamber 67, while the bread rack 70 is disposed in the toastingchamber 68. Essentially, the toast racks 69 and 7 0 comprise centralrodlike supporting members, extending transversely of the toastingchambers 67 and 68, respectively. These rod-like members are illustratedas supporting a plurality of V-shaped fingers 71 disposed in spacedrelationship with the open ends of each V extending upwardly so as totend to center the sliced material being toasted regardless of thethickness of the slice which can readily be accommodated between theguide wires 36.

For the purpose of relating the bread racks 69 and 70 into a unitarystructure, there are provided along the outside of the frame andsubstantially parallel with the side frame plates 46 and 47 a pair ofhorizontally disposed bread rack side arms 72. Each of the ends of thebread racks 69 and 70 are adapted to extend beyond the side frame plates46 and 47 which are provided with substantially vertically extendingslots 74 and 75 for the purpose. As illustrated, the ends of the breadrack 69 extend outside the frame 45 through the vertical slots 74 whilethe ends of the bread rack 70 extend outside the frame 45 through thevertical slots 75. These slots 74 and 75 extend to the bottom of theside frame plates 46 and 47, whereupon the bread racks 69 and 70 whichhave their ends fastened to spaced points on the side arms 72, as byspot welding or the like, may be assembled and insorted into the slots74 and 75 before the subbase is attached to the side frame plates 46and47. The slots 1 74 and 75 are illustrated as being slightly curved toaccommodate the movement of the bread carriage including the bread racks69 and 70. The slots 74 furthermore extend much closer to the tops ofthe side frame plates 46 and 47 than the slots 75 to accommodate certaincontrol mechanism described hereinafter.

In order to form a rigid unitary bread carriage, the ends of the rackside arms 72 adjacent the thermostat end of the automatic toaster 25which is remote from the slot 75 are interconnected by a bread. rackyoke 77 suitably fastened thereto by any suitable means such as thescrews 78. As illustrated, each of the ends of the side arms 72connected to the yoke 77 are provided with an integral cross member 72aso as to form with the associated side arm a somewhat T-shaped member.Similarly, the ends 'of the bread rack yoke 77 are provided withintegral cross members 77a which interfit with the cross members 72a toprovide at each end of the bread rack yoke 77 three vertical spacedopenings.

It will be understood that by employing the interfitting crossmembers72a and 77a, assembly therewith of elements disposed in such verticallyspaced openings is great- 1y facilitated.

It will, furthermore, be understood that the bread carriage comprisingmembers 69, 70, 71, 72, 77 and 78, and generally designated by thereference numeral 79, should be maintained in a substantially horizontalposition, so that the bread racks 69 and 70 are maintained insubstantially the same horizontal plane at all times. In order to guideand support the carriage 79 for vertical movement while maintaining thebread carriage 79 in a horizontal plane, there are provided two pairs ofpivotally mounted parallel motion arms 80 and 81 of substantiallyidentical configuration which are pivoted to the frame 45 at the cordend of the automatic toaster 25 and connected to the bread carriage 79at the thermostat end of the toaster.

As illustrated, each pair of the parallel motion arms 3 and 81 are inthe form of a closed loop of wire completely surrounding the frame 45and having a particular configuration closely conforming to the framecross section clearly shown in Fig. 7 of the drawings.

To pivotally support the parallel motion arms 81 and 82 at the cord endof the automatic toaster, the angular extensions 46a and 47a of the sideframe plates 46 and 47 are each provided with projections 46b and 47bextending beyond the end top frame plate 52, which projections aredisposed in spaced parallel relationship. The vertical edges of theprojections 46b and 47b each are provided with vertically spaced notches83 and 84 for pivotally supporting the parallel motion arms 80 and 81,the notches 83 being adapted to receive portions of the arms 80 whilethe notches 84 are adapted to receive portions of the arms 81. For thepurpose of maintaining the parallel motion arms 80 and 81 in theirrespective notches 83 and 84 and at the same time strengthen the frame45 by interconnecting the side frame plates 46 and 47 at the cord endthereof, there is provided a frame cross yoke 86. This yoke 86 issuitably fastened by means of self-tapping screws 87 engaging lateraltabs 86a, integrally formed from the frame cross yoke 86, and theprojections 46b and 4712.

In order to limit sidewise movement. of the parallel motion arms 81 and82 within the notches 83 and 84, each arm is provided at its pivotallymounted end between the notches 83 and 84 with a small U-shaped benddesignated as 80a for the loop 80 and similarly as 81a for the loop 81.These U-shaped bends 80a and 81a are disposed in notches cut in theupper and lower edges respectively of the cross frame member 86 near thecenter thereof. The vertical edges of these notches are formed into ears89 clearly shown in Fig. 7 of the drawings, to engage with either sideof the U-shaped bends 80a and 81a, respectively, thereby limitingsidewise movement thereof. This arrangement tends to reduce bearingfriction due to pivotal mounting of the parallel motion arms 80 land 81,since the ears 89 are bent so as to engage the U- shaped bends 80a and81a at points coaxial with the hearing points of the arms 80 and 81 innotches 83 land 84, respectively.

Preferably the parallel motion arms 80 and 81 are originally formed intoclosed loops from suitable wire stock and at the junction of the ends ofeach loop there are provided a pair of spaced washers 83 indicated atone side of the cross portions thereof near the thermostat end of thetoaster 25. These thermostat end cross portions designated as 8812 and81b, respectively, for the parallel motion arms 88 and 81, respectively,are bowed sufficiently to clear any mechanism at the thermostat end ofthe toaster in moving from the position shown in Fig. 3 to the positionshown in Fig. 4 of the drawings. The parallel motion arms 80 and 81 arepivotally related to the bread carriage 79 by extending through theuppermost and lowermost openings, respectively, of the three verticallyspaced openings referred to above, defined by the interfitting crossmembers 72a and 77a. The washers 83, as is clearly shown in Figs. 3 and7 of the drawings, are disposed on either side of one set ofinterfitting cross members 72aarid 77a to prevent other than relativepivotal movement between the bread carriage 79 and the parallel motionarms 89 and 81. From the above description it is apparent that by virtueof the parallel motion arms 80 and 81 the bread carriage 79 isconstrained to move only in a vertical direction and the bread racks 69land 70 are maintained in substantially the same horizontal planethroughout the motion thereof.

For the purpose of limiting the maximum motion of the bread carriage 79so that the desired movement of approximately three inches of the breadracks to and from the toasting position is produced, the vertical crossmembers 72a are provided at their upper and lower ends with lateralprojections 7212, the upper ones of which engage with suitable integralextensions or stops 88 projecting from the thermostat end of the sideframe plates 46 and 4'7, respectively. The maximum downward movement islimited by the lower lateral projections 72b of the bread carriage 79coming into engagement with the subbase 50. The uppermost position ofthe bread carriage 79 is shown in Figs. 3 and of the drawings where thestops 88 are engaged thereby. The lowermost position of the breadcarriage is shown in Fig. 4- of the drawings where the subbase 51) isengaged thereby.

Motion multiplying means It will be understood that any suitable motivemeans for causing movement of the bread carriage 79 may be provided.Such means might comprise an electric motor such as is disclosed in theabove-mentioned Wright and epson patent, spring motive means or thelike. As described in detail in the ensuing description, there isprovided a thermemotive means 60 Which acts as the prime mover for thebread carriage 79. This thermomotive means on is capable of producingonly a limited amount of movement of the lifter lever depressor bar 58of the order of about one-eighth of an inch, as will be described indetail hereinafter. in order to convert such limited vertical motion ofthe depressor bar 53 to the desired movement of the bread carriage 79, asuitable motion multiplying means is required to interconnect thedepressor blar 5S and the bread carriage 79. As illustrated, thismechanism comprises a U-shaped lifter lever 90 and a lifter lever yoke91. The lifter lever 96 is preferably disposed so that the arms 99a ofthe U are in a generally horizontal position and are parallel with theside frame plates 46 and 47. Furthermore, the bight of the U extendsacross the cord end of the frame beneath the projections 46!; and 4717.The arms 90a are preferably pivotally mounted at intermediate pointsthereon to the frame 4-5 by means of pivot pins 93 in the form ofsuitable screws, or the like. The ends of the arms 9% of the lifterlever 9% remote from the bight of the U are pivotally connected by meansof a rivet 94 adapted to be engaged by upwardly extending hooloshapedportions 58a of the depressor bar 58.

The lifter lever yoke 91 comprises a channel-shaped cross member llaextending across the cord end of the frame .-5 beneath. the projections46]) and 47b. Integrally formed with each end of the cross member 91aare vertically disposed links 95, the lower ends of which are pivotallyconnected by pivot pins 96 with the bight end of the U-shaped arms 9% ofthe lifter lever $1M The upper ends of the links 95 are provided withnotches 97 for receiving therein portions 81c of the parallel motionarms till, which are parallel with the cross member S ice so as to becapable of raising the parallel motion arms fill and 81 in response toupward movement of the links $5. Since the links 95 are capable oftransmitting upwardly directed forces to the parallel motion arms 31 atpoints close to the notches 84 which pivotally support the arms (31, itis apparent that the forces are transmitted through very short leverarms, and, consequently, a small vertical movement of the links 95 andconsequently of the portions 810 of the arms 81 causes a much greatermotion of ends of the arms 81 supporting the breadcarriage 79. In amechanism constructed in accordance with the present invention, a motionmultiplication of approximately twenty-two to one was obtained, whichmeans'that a one-eighth inch vertical move ment of the links 95 producesapproximately three inches of movement of the bread carriage '79.

The employment of a means for producing such a large motionmagnification calls for the application of a relatively large force tothe depressor bar 58 to produce sufficient force at the bread carriageto move it against the stops 88 when supporting two slices of toast. Theweight of the bread carriage will, of course, cause it to move to itslowermost position when not opposed by a force applied through the links95 and the parallel motion arms til. it is important, therefore, thatthe motion multiplying means described above be substantiallyfrictionless. The friction free requirement is very important, sinceotherwise jumpy and erratic bread carriage motion would result. it willbe understood that, due to the very high temperatures at which toastersoperate, lubricated bearing points are entirely unsatisfactory, and itwould furthermore be undesirable to require an operator to lubricatesuch bearing points periodically, particularly since many of them arequite inaccessible. In accordance with the present invention frictionhas been reduced to an absolute minimum by completely eliminating allsliding friction at the bearing points and replacing it with rollingfriction. To this end the lifter lever is provided with rectangularopenings 99 and 101 (see Fig. 5) for the pivot pins )3 and 96,respectively, thereby providing flat bearing surfaces of sufiicientlength to permit the necessary limited rolling of the pivot pinsrelative to the cooperating flat surfaces. The effective flat surfacesof the rectangular openings 99 are the top surfaces, while the bottomsof the openings 101 provide the effective flat surfaces, as is clearlyshown in Fig. 5 of the drawings. The top engaging surfaces Hill of thehook-shaped members 58a are flat, as is clearly shown in Fig. 5 of thedrawings. ln addition, the notches 83 and 34 are provided with flat topsurfaces of greater length than the diameter of the Wire from which theparallel motion arms 55% and 31 are formed to permit rolling friction ofthe parallel motion arms and 81 relative thereto. Also, the notches 97in the links are provided with fiat surfaces at the bottom thereof whichare substantially longer than the diameter of the engaging portions 810of the parallel motion arms 81 to permit the desired rolling friction.In all of these cases the flat surfaces for insuring rolling frictionare designed so as to be normal to the direction of bearing pressure. Itwill be understood that if when the toaster is first put into operationand by accident oneor more of the bearing shafts are at the wrong end ofthe flats, sliding friction would occur until the shaft properlypositions itself en the fiat. After this initial sliding friction thepressure remains sulficiently high that the bearing shafts remainproperly positioned on their respective flats, so that thereafter a purerolling friction occurs at the bearings.

Thermomotive prime mover for bread carriage As was mentioned above, asuitable motive means for causing movement of the bread. carriage 79must be provided. -Heretofore such means have comprised spring motors,electric motors and the like. Since automatic toasters require largeamounts of electrical energy to perform the toasting operation (1100watts or more) it was thought desirable to take advantage of thethermomotive etfect which can be produced by the expansion andcontraction of a metal due to change in temperature thereof. Inaccordance with the present invention a series of spaced 'turns of wirehaving a small surface area which can be obtained. Unfortunately, theactual motion obtainable with such a wire, even with a large temperaturerise, is relatively small, and in accordance with the present inventionan eificient and reliable motion multiplying means is provided, wherebythe thermo. motive device 60 produces the necessary movement of thedepressor bar 58. Referring now to Fig. 8 of the drawings, there isillustrated the thermomotive device 60 comprising a plurality of spacedturns of a nickel chromium wire generally designated as 103. For thepurpose of multiplying the motion produced by virtue of the change inlength of the different turns or loops of the wire 103 when heated bycurrent flow therethrough, the thermomotive device 60 comprises anexpansible support in the form of spaced insulated vertical structuresaround which the turns of the resistance wire 103 are wound, whichstructures in turn are supported by specially shaped yokes or trussesformed from thin stainless steel spring stock. As illustrated, thespaced vertical structures comprise a pair of channel or U-shaped strutmembers 106 disposed with the closed ends or bights of the U towardseach other. These vertical strut members are provided with openings 107in order to make them as light as possible without appreciably reducingthe rigidity thereof. The upper ends of the struts 106 areinterconnected by a V-shaped truss or yoke 108 having a relativelyshallow angle, i. e., the angle defining the V is approximately 150. Asa consequence, a very small change in the lengths of the loops of theresistance wire 103 due to expansion under the application of heatpermits a relatively large vertical motion of the center of the truss oryoke 108 even though the ends thereof move very slightly in a horizontaldirection. The V- shaped truss 108 is designed with an unflangedrelatively horizontal centralportion 108a and untlanged horizontal endportions 108b. These portions 108a and 1085 are interconnected byflanged angularp'ortions 1000, as is clearly shown in Figs. 7 and 8 ofthe drawings. Flexing or bending of the truss 108 can, therefore, onlyoccur in the unflanged central portion 108a or the unfianged endportions The truss 108, due to the weight of the bread carriage,inherently tends to straighten out and continually exerts. a forcetending to separate the strut members 106, which action is restrained bythe turns of the resistance wire 103.

In order to connect the upper ends of the struts 106 with the ends 108bof the truss or V-shaped yoke 100, the struts 106 are provided withintegral extensions 109 which extend through suitable openings definedin the ends 108a of the truss 108 and through openings in truss washers110, which extensions 109 are peened over as indicated thereby fixedlyto interrelate the struts 106 and the truss 108.

In order further to multiply the limited relative move ment of thestruts 106 by virtue of the expansion and contraction of the resistancewire 103, the lower ends of the struts 106 are similarly interconnectedby two spaced trusses 112 and 113 which are very similar to the truss.108. Two trusses are employed to prevent skewing of the frame definedby the struts 106 and the trusses 100, 112 and 113 under the tensileforce due to the resistance wire 103 wound thereon. As illustrated, thelower ends of the struts 106 are provided with sutficiently longprojections 114 to extend through suitable openings in the horizontalunflanged ends of the trusses 112 and 113 as well as through washers115a and spacers 115b. The ends of the projections 114 are peened overfixedly to interrelate the ends of the trusses 112 and 113 with thelower ends of the struts 106. The trusses 112 and 113 are provided withunfianged central portions supporting a center adjusting screw bushing116 and flanged intermediate portions substantially identical with thetruss 108. A suitable truss spacer 117 maintains the central portions ofthe trusses 112 and 113 in spaced relationship. in one arrangementconstructed in accordance with the present invention, the yoke 108 wasdesigned so that the horizontal ends 108k thereof were displacedvertically from the center portion 108a by substantially three-eights ofan inch when the resistance wire 103 was cold, thereby affording theabove-mentioned very shallow angle. Under the same conditions, in aconstruction embodying the present invention, the ends of the yokes 112and 113 were disposed vertically above the central portions thereof bysubstantially five-sixteenths of an inch.

In addition to the double truss arrangement at the lower ends of thestruts 106 which prevent skewing in one direction of the frame of thethermomotive device 60 (comprising the struts 106 and the trusses 108,112 and 113), the upper end of one strut 106 is connected by means of asuitable tension wire 118 with the lower end of the other strut 106 toprevent skewing in another direction. The ends of this diagonallydisposed wire 118 may be hook-shaped to engage suitable slots defined inthe upper and lower ends of the bights of the U-shaped struts 106, as isclearly indicated in Fig. 8 of the drawings.

To properly support the turns of the resistor wire 103 in the form of aspiral on theframe of the thermomotive device, in spaced relationshipand insulated from the frame there are provided on each side of theframe two vertically disposed insulating strips 120 and 121 which areprovided with suitable notches for receiving integral extensions 122 ofthe struts 106 to prevent vertical movement of the strips 120 and 121relative to the'struts 106. Movement thereof in any other direction isprevented by the turns of the resistance wire 103 wound thereabout. Theinsulating strips 120 may be designated as the clip insulators forinsulating a plurality of wire receiving clips 123 from the struts 106.The wire receiving clips 123 are preferably supported in verticallyspaced notches defined in the insulating strips 121. The wire receivingclips 123 are U-shaped and maintain the individual turns of theresistance wire 103 in properly spaced relationship relative to eachother. The turns of the wire 103 also aid in holding the clips 123 inposition in the notches defined in the insulating strips 121.

The lower end of the resistance wire 103 is suitably fastened to aterminal bolt 125 which extends through the lower end of one of thestruts 106 whereby suitable electrical connection can be made therewith.Similarly, the upper end of the resistor wire 103 is connected to asuitable terminal bolt 126 extending through the upper end of the struts106 whereby electrical connection can be made thereto. As illustrated,the ends'of the resistance wire 103 are disposed within suitable slotsprovided in the heads of the terminal bolts 125 and 126, respectively,and brazed or soldered thereto.

It should be understood that the thermomotive device 60 may be supportedin any suitable place within the automatic toaster 25 so that therelative movement between the central portions 108a and 112151 of thetrusses 108 and 112 may be transmitted to the depressor bar 58. If thisdepressor bar 58 is located near the center of the toaster, asillustrated, then the thermomotive device must preferably also belocated centrally of the toaster. It will be apparent, however, that thedepressor bar 58 might equally well be disposed near one end of thetoaster, as, for example, the cord end, in which case the thermomotivedevice 60 could also be disposed at such end. The electrical energyrequired to heat the resistance wire 103 of the thermomotive device 60is wasted except for the mechanical work obtained in producing relativemovement of the centers of the trusses 108 and 112. On the other hand,no mechanical work is obtained from the toasting elements employed inconventional automatic toasters which ordinarly use 1100 or more wattsof electrical energy. In the copending Loomer application, Serial No.11,646, filed February 27, 1948, now Patent No. 2,590,334, and assignedto the same assignee as the present application, there is disclosed andclaimed an arrangement in which the thermomotive device of the presentinvention with minor changes also functions as one of the toastingelements of the automatic toaster. This is very desirable, since thehigh electrical energy required for toasting is more than sufiicient toproduce the desired mechanical work of the thermomotive device.Accordingly, the thermomotive device of the present invention has beenillustrated in this preferred embodiment whereby the resistor wire 103also acts as the center heating element of the automatic toaster 25disposed between the toasting chambers 67 and 68. To this end, thecentral portion 108a of the truss 103 is rigidly fastened as by means ofa bolt 127 to the center top frame plate 53. So that the flangedportions 1693c of the yoke 100 do not interfere with the center topframe plate 53, the frame plate 53 is provided with a central depressionto which the bolt 127 is fastened. The center top frame plate 53 isfurthermore provided with depending projections 53c preferably punchedtherefrom, as is clearly shown in Figs. 7 and 8 of the drawings. Theseprojections 53c are adapted to engage the ends 103a of the yoke or truss103 to limit their maximum upward movement and consequently prevent theyoke 108 from snapping over center. With this arrangement the center100a of the truss 108 is fixed and consequently all movement occurs atthe bushing 116. In order to depress the depressor bar 58, there isprovided a stud or center adjusting screw 1.28 threadedly engaged withthe bushing 116. This stud is provided adjacent its lower end with ashoulder 129 engaging the depressor bar 58 and including a slottedprojection 130 extending through a suitable opening defined in thedepressor bar 58. By means of the stud 128, suitable adjustment of themotion transmitted to the depressor bar 5'3 by the thermomotive device60 may be controlled.

If the thermomotive device 60 is also employed as the center heatingelement, then preferably a center element barrier plate is provided toconfine a portion of the heat produced by the resistor wire 103 to eachof the toasting chambers 67 and 68 in case a single slice is beingtoasted. Such a barrier plate may comprise two very thin reflectorplates 131, one disposed on either side of the Wire 118 which may beused to support the same. if desired, an additional wire 132 may extenddiagonally between the reflector plates 131, as clearly indicated inFig. 8 of the drawings, to better support the barrier plate. The ends ofthe wire 132 may extend into notches in the bights of the U-shapedstruts 1% adjacent the ends thereof similar to the notches for receivingthe hook-shaped ends of the wire 11%. The center element barrier plate131 has no function as far as the thermomotive device of the inventionis concerned, but is employed only when the thermomotive device alsoacts as the center heating element. Where the resistance wire 103 of thethermomotive device 50 is employed also as a toasting element, the turnsof wire near the bottom are spaced more closely than at the top, as isclearly illustrated in Fig. 8 of the drawings, in order to obtain moreuniform toasting. This is necessary because of the fact that the breadslices are heated by convection as Well as by radiation.

The operation of the thermomotive device es of the present inventionwith respect to the bread carriage 79 wiil be understood in view of thedetailed description included above. The operation is described indetail in Koci Patent No. 2,667,828, beginning at line 50 of column 15,and is not repeated here since the elements and reference numerals areidentical in the instant applicationand in the above-mentioned Kocipatent.

By employing the resistor wire 103 of the thermomotive device in a dualcapacity both as a toasting or heating element as well as the means forproducing mechanical work as is claimed in the above-mentioned copendingLoomer application, adequate lifting power for the bread rack 79 isprovided without requiring any additional expenditure for electricalpower. Furthermore, the mechanical arrangement is relatively simple andto a large degree is self-compensating for variations in manufacture.Thus, if one loop of the spirally wound resistor wire 103 happens to bewound tighter than the remainder and as a consequence assumes more thanits share of stress, it will yield as that stress become excessive andtransfer some of it to the other loops of the wire. Actually thethermomotive device 60 is designed to provide for two and one-half tothree times as much movement as is actually used. The main reason forthis is to provide a reasonably rapid and uniform rate of movement ofthe bread carriage 70. A second reason is to free the loops of the wire103 of stress after their temperature exceeds what is considered a safelimit of between 1100 to 1200 F. When current is passed through theheater wire 103, its temperature rises with time approximately inaccordance with the exponential law:

T=T;(1e"') Also, in cooling the temperature varies approximately inaccordance with the following expression:

where T represents the instantaneous value of temperature, Tr representsthe equilibrium high temperature (both such temperatures being relativeto the surrounding or ambient temperature), e is the natural logarithmicbase, t represents time, and k is a constant. Actually, the temperaturerise departs somewhat from that indicated by the above equations becauseof the fourth power rela tionship between absolute temperature and heatdissipated as radiant energy.

On the fairly accurate assumption that an exponential law issubstantially followed, reference may be had to Fig. 21 of the drawingswhere there is illustrated a curve diagram X in which the temperaturerise and fall of the resistance wire 103 is plotted with respect totime. It is also assumed that the expansion coeflicient of theresistance wire 103 is uniform within the range of temperatures that thewire is subjected to and that the motion multiplication factor remainsconstant. On these assumptions the curve X of Fig. 21 indicates not onlythe temperature change of the resistor wire 103 with time, but also thecorresponding available motion of the bread carriage 79 with respect totime. Referring now to the curve diagram Fig. 21, it may be noted thatthe available movement of the carriage 79 upon heating of the resistorwire 103 is represented by the vertical distance from O to C. Theactually used movement in a properly adjusted thermomotive device suchas 60 is represented by the vertical distance from A to B. It isapparent at once, therefore, that the time allowed for the bread carrierto move from a position corresponding to A to a position correspondingto B is very much less than the time required for heating the element103 from room temperature to a temperature approaching its finaltemperature. Further in the range from A to B the temperature riseapproaches a straight line relationship, which means that the rate ofrise and, consequently, the velocity of movement is substantiallyuniform in this range, whereupon the bread slice is caused to move at auniform rate of speed within the actual range of motion. As a result ofall this, when the resistance wire 103 heats up dining the periodrepresented by the range from O to A in Fig. 21 of the drawings, the netresult is simply a gradual release of the pressure of the bread carriage79 against the stops 88. As the temperature of the resistance wire 10313 passes beyond the point A of the curve X, downward movement of thebread carriage 79 results. When the resistance wire 103 reaches atemperature of the order of 1100 F., the bread carriage 79 engages thesubbase 50 which limits its maximum downward movement so that subsequentheating of the resistor wire 103 causes the individual turns to expandthereby removing any stress on them due to the weight of the breadcarriage and the bread slices being toasted, since this weight issupported by the subbase 50 which is now engaged by the bread carriage.The point C in Fig. 21 represents the final temperature of about 1600F., and in this highest range of temperature from 1100 to 1600 theresistance wire 103 is under no more longitudinal stress than in anyconventional toasting element.

Upon cooling of the resistor wire 103 from the point C to B of the curveX, no resultant movement of the bread carriage 79 occurs and itcontinues to engage its lower limit stop, namely, the subbase 50. As isobvious from the curve of Fig. 21, the time of cooling during this rangeis very short so as to be substantially negligible. At the point B theresistance 103 has cooled and contracted sufliciently to begin toencounter'the stress applied through the yokes 112, 113 and 108, and thestruts 106 of the weight of the bread carriage 79 and the bread slicescarried thereby, and from B to A the contraction of the resistor wire103 causes relative separation of the center points of the trusses oryokes 108 and 112, with the result that the depressor bar 58 is moveddownwardly to lift the bread carriage 79 and associated bread slicesfrom the position shown in Fig. 4 of the drawings to the position shownin Fig. 3. From the point A to O the resistance wire 103 cools stillfurther and more slowly, as is clearly indicated by the curve X, but nofurther movement of the bread carriage 79 results since such movement isprevented by the stops 88. Instead, further contraction at theserelatively low temperaturesof the resistance wire 103 serves to increasethe pressure of the bread carriage 79 against its upper stops 88. Thispressure involves the application of a considerably greater stress onthe resistance wire than that due to the weight of the bread carriagealone. This pressure may be adjusted by means of the center adjustingscrew 128, and it should at least equal the weight of two bread slicesof the largest size which could be accommodated by the automatic toaster25 so that when such bread slices are placed on the bread carriage 79suflicient force will still be present to hold the bread carriageagainst the stops 88 until the thermomotive device 60 functions topermit movement to the toasting position.

It will be understood that if someone were to forcibly depress the breadcarriage 79 while the heater wire 103 was cold, an increased stresswould be applied thereto. If desirable, a suitable relief spring couldbe provided to relieve such additional stress on the wires. However,this has been found to be unnecessary due to the high resilience of thestructure, especially in the parallel motion arms 80 and 31, whereuponsuch additional stress is only partially transmitted to the turns of theresistance wire 103 even under such abnormal conditions. Furthermore, atthese low temperatures (room temperature) the resistance wire 103 isable to withstand much higher stresses than when heated well above 1100F. If, for example, the toaster were incorrectly adjusted at the factoryso that the bread carrier motion is shifted from its proper range AB tothe higher temperature portion of the curve X of Fig. 21 of the drawingswhereby an excessive stress would be applied to the resistance wire 103when hot, this condition would automatically correct itself. Suchstress, if excessive, would cause the wire 103 to yield slightly, and inso yielding will bring the useful portion of the curve within the rangeA-B where it belongs.

The stress on the resistor wire 103 can be further reduced by applying atension spring between the subbase 50 and the U-shaped bend 81a of theparallel motion Cit arms 81. This spring, if properly designed, can. bemade to partially offset the weight of the bread carriage and associatedparts. In an arrangement constructed in accordance with the presentinvention and designed for 115: volt operation, it was found that thestress due to the weight of the bread carriage 79 was sufficientlybelow, the safe value of stress on the wire 103 so that the spring,mentioned above was unnecessary. However, in designing a model forhigher voltages, as for instance 220 volts, where the heating elementmust of necessity be of much smaller cross section, it may be necessaryto add such a tension spring.

Specially shaped dual linear heat sources From the above discussion itis apparent that the resistor wire 103 also functions as a centerheating element for toasting one side of any bread slices disposed inthe toasting chambers 67 and 68. To toast the other sides of the breadslices, so called end toasting elements? are conventionally providedwhich would be disposed at the thermostat end and the cord end of thetoaster adjacent the toasting chambers 67 and 68, respectively. Beforedescribing the end toasting elements of the present invention, attentionis directed to the fact that the automatic toaster 25 employs theradiation control principle of the above-mentioned copending Kociapplication whereby a therm-oresponsive device is dependent upon thesurface temperature of a substantial area of the bread surface beingtoasted. My invention contemplates collecting a large amount ofradiation emitted from a substantial area of the bread surface beingtoasted and applying the same to a bimetallic element or the likeWithout permitting such bimetallic element or thermostat to receive anyheat energy radiated from the toasting elements. I have observed thatthe total radiant energy emitted from the bread surface by virtue of itstemperature rise is relatively small and the radiant power is measuredin milli- Watts, and I have found also that for reliable operation on,this principle it is necessary to collect and direct as large an amountof this energy as possible on (the thermal control element.Consequently, conventional toasting elements such as the resistance wire103 associated with it would be difiicult to provide an arrangementwhereby direct radiation therefrom is not received by the bimetallicelement and still wherein the heat: energy radiated from a large surfacearea of the bread surface being toasted is supplied to the element.Accordingly, it is necessary to provide an end toasting element for thethermostat end of the toaster 25 which provides uniform. toasting overthe entire bread surface While still permitting a large amount ofradiation from a substantial area.

of the bread surface being toasted to reach the thermal control devicedisposed at the thermostat end of the toaster without permitting directradiation from such end toasting element to reach said device.

Since it is conventional in automatic toasters to control the toastingoperation of a two slice toaster in dependence upon the actualconditions afiecting only one of the two slices, this feature isembodied in the automatic toaster of the present invention.Consequently, when only a single bread slice is to be toasted, it mustbeinserted in the toasting chamber 67 adjacent the thermostat end of thetoaster. If a single slice is toasted and inserted in chamber 68,nothing will happen, so the operator will immediately become aware ofthe fact that it should be inserted in the other toasting chamber. Withsuch an arrangement it will be apparent that only one of the endtoasting elements, namely, the one at the thermostat, end, need be ofthe special construction referred to above and described in detailhereinafter. As illustrated in the drawings, however, substantiallyidentical end heating units are provided primarily to reduce the numberof difierent parts required, since, as will be understood from the scentabove discussion, the central heating element is of necessity of specialconstruction. 7

In accordance with the present invention, and as disclosed and claimedin a divisional application now Patent No. 2,590,328, the end heatingunits each include a pair of linear heat sources comprising spaced apartvertically disposed resistor elements so as to afford a substantial areatherebetween to permit heat radiated from the surface of thebread slicebeing toasted to reach a suitable thermal responsive control device. Asillustrated, the two heating elements of each end heating unit areidentical and, for reasons described in greater detail hereinafter,comprise a resistor wire wound in the form of an elliptical spiral abouta core of strip insulating material with the narrow diameter of theelliptical spiral being disposed parallel to the bread slices andconsequently the toasting chambers 67 and 68. The heating elements ofthe thermostat end toasting unit are designated as 140a and 140b,respectively, while the heating elements of the cord end toasting unitare designated as 141a and 141b, respectively. These heating elementsare designated schematically in Fig. 19 of the drawings and are shown indetail in Figs. 7, 15, 16, 17 and 18.

For the purpose of supporting the heating elements 140a, 140b, 141a and141b of the end heating units, each end heating unit is in the form of aunitary assembly comprising in addition to the heating elements suitablesupporting and reflecting devices. Considering first the cord endheating unit generally designated in Fig. 15 of the drawings by thereference numeral 142, it may be noted that it comprises in addition tothe heating elements 141a and 141b a combined reflector and support 143whose effective reflector surface is a plane surface. Preferably thereflector 143 is formed of bright rolled aluminum or the like and isprovided with a pair of spaced integral downwardly extending projections143a at the lower edge thereof and similar integral upwardly extendingprojections 144 at the upper end thereof. In order to provide sufficientstrength, the reflector 143 is preferably provided with verticallyextending flanges 145 at the edges thereof and horizontally extendingribs 146 adjacent the upper and lower horizontal edges thereof, whichribs preferably include extensions into the projections 143a and 144, asis clearly shown in the drawings.

To support the reflector M3 at the cord end of the automatic toasterparallel to the toasting chamber 68, the subbase is preferably provi edwith suitable openings Silc to receive the projections 143. Similarly,the cross top frame plate 52 is provided with openings 5% (see Fig. 7 ofthe drawings) for receiving the projections 144. With this arrangementit will be apparent that the heating elements 141a. and 14th aresuitably supported from the reflector 143 and the heating unit 142 isfirmly supported by the toaster frame adjacent the toasting chamber 68.Although the heating elements 141a and 14111, and similarly the heatingelements 146a and 14%, are illustrated as being vertically disposed,they could equally well be disposed in horizontal planes and stillprovide the necessary space therebetween for permitting heat energyradiated from the surface of the bread slice being toasted to reach thethermal responsive device which permitting the employment of simplemeans for preventing the radiant energy from the heating elementsthemselves from reaching the thermal responsive device. The verticaldisposition of the heating elements is believed to be preferable in thatthey are less likely to provide a ledge for catching crumbs and alsothey readily permit variation in spacing between adjacent turns toprovide for convection heat transfer which is aiways present when theelements are spaced from the material to be heated. For this reason thevertical arrangement is disclosed in the drawings and, furthermore, thehealing ele- 16 ments a, 1401;, Mia and Mlb have the lowermost turnsthereof spaced more closely together than the upper turns, as is clearlyshown in Figs. 15 to 18 of the drawings, in a manner similar to thecenter heating element m3 disclosed in Fig. 8 of the drawings.

In order to support the heating element 141a, a pair of brackets 148 areprovided spaced vertically from each other and suitably riveted to thereflector 143 by means of rivets 149. Since the brackets 148 arepreferably employed both as a mechanical support for the heating elementassociated therewith as well as electrical connections for the terminalsthereof, suitable insulating washers and bushing arrangements 15%) and15.1 are provided, as is clearly shown in Fig. 16 of the drawings.Identical brackets 148 and fastening means therefor are provided for theheating element 1411b. The ends of the heating elements 141a and 141i)are preferably bent into the form of hooks which are hooked over thebrackets 148, as is clearly shown in Fig. .16 of the drawings, and arepreferably spot welded thereto to insure proper mechanical support aswell as satisfactory electrical connection thereto.

In order that the reflector 143 may be effective uniformly to reflectheat energy radiated from the entire vertical extent of the heatingelements Mia and 1411!), it is desirable that the heating elements beuniformly spaced from the reflector. To insure such uniform spacing,there is preferably disposed within the turns of the heating elements141a and 14112 a suitable core in the form of a strip of insulatingmaterial 153 with the narrow dimension of the strip being directedtoward the reflector 143. This strip will prevent bending of the heatingelements in a direction toward and away from the reflector 1A3. Bendingof the elements 141a and Mill) in the other direction will not adverselyaffect the heating thereof in the same manner as bending in thedirection prevented by the strips 153. These elements 141a and 14117 maybe initially wound on this strip to present the spiral winding ofelliptical cross section. I

The heating elements 140a and 149i) associated with the thermostat endheating unit generally designated at 155 in Fig. 17 of the drawings issubstantially identical with the heating unit 142 and comprises asimilar piane reflector 156 having downwardly extending projections 1.57engageable with openings 50d defined in the subbase 542, and projections158 at the upper end thereof engageable with openings Sib in the topcross frame member 51. Suitable brackets 159 identical with the brackets148 are fastened in an insulated manner to the reflector 156 by means ofrivets ieil and insulating washers 161 and 1.62. The reflector 156 isfurthermore provided with vertical flanges 163 to give strength andrigidity thereto, and, in addition, suitable horizontal ribs 164 areprovided adjacent the upper and lower edges thereof which haveextensions leading into the projections 15'? and 358. Each of theheating elements Main and 149:; preferably is wound on a core 165 in theform of an insulating strip identical with the insulating strips 1515described in connection with the heating unit assembly 142.Substantially the only difference between the heating unit assemblies142 and 1155 resides in the design of the reflector 1156 of the heatingunit assembly 155, which includes a rectangular opening 1'68 thereinbetween the heating elements 140a and 14Gb which, as will becomeapparent from the following description, provides a window of relativelylarge opening for collecting the energy radiated from the surface of thebread slice being toasted in the toasting chamber 67 and direct it tothe main portion of the thermostat. The means for preventing radiantenergy from the heating elements Edda and 1.4%!) or the central heatingelement 103 from reaching the thermostat end of the toaster 25 andaffecting the thermal responsive device associated therewith will bedescribed in greater detail hereinafter although they are preferablyassociated with the reflector 156.

1. ELECTRICAL CIRCUIT It will be understood that any suitable means ofsupplymg electrical energy to the heatingelements 103, 140a, 1401),141a, and 141b may be provided. These individual heating elements may beconnected in parallel, in series, or in some sort of series-parallelcombination. The particular manner of supplying them with electricalenergy may best be understood by reference to Fig. 19 of the drawingswhere the heating elements are schematically illustrated and designatedby the same reference numerals as in the structural figures of thedrawings. As illustrated, the heating elements are all connected inseries with one another and to a suitable source of power through aconventional appliance cord 170 which includes the wellknown plugconnector 171 for connection to any suitable electrical outlet. Asillustrated in Fig. 19 of the drawings, the electrical circuit comprisesin addition to the heating elements a single control switch generallydesignated as 172, and comprising relatively movable contacts 173 and174 to be described in greater detail hereinafter. When the contacts ofthe control switch 172 are open, the circuit through the seriallyarranged heating elements is interrupted. Conversely, when the switch172 is closed, the circuit through the serially arranged heatingelements is closed, and if the plug connector 171 is connected to asuitable source of energy, current will flow through the heatingelements in a well understood manner. Because it is not common practiceto supply direct current as the source of electrical energy, and becauseof the added cost of a structure having a switch suitable for bothalternating and direct current operation, the illustrated embodimentincludes a switch suitable for alternating current only.

For the purpose of serially interconnecting the various heatingelements, suitable bus bars are provided which are preferably disposedin the automatic toaster was to be suitably spaced from any adjacentconducting portions for satisfactory insulation therefrom, andfurthermore so as not to interfere with any of the moving parts of thetoaster as well as to be free of the toasting chambers and the like. Tothis end the upper end of the toasting element 14% is connected by meansof a suitable bus bar 176 with one terminal of the switch 172 to bedescribed in greater detail hereinafter. Preferably the bus bar 176 isconnected to the upper bracket 159 associated with the heating element14Gb by means of the same rivet 160 that supports the bracket from thereflector 156. The lower endsof the heating elements 140a and 14011 areinterconnected by means of a bus bar 177, as is clearly shown in Figs.17 and 18 of the drawings. To interconnect the upper end of the heatingelement 140a and the upper end of resistor wire 103, there is provided asuitable bus bar 178 having one end thereof suitably connected by meansof the rivet 160 to the upper end of the heating element 140a and theother end suitably connected to the terminal bolt 126, as is clearlyindicated in Figs. 7 and 8 of the drawings. It will be understood thatsince the bus bar 178 is disposed adjacent the upper end of theautomatic toaster and extends from the thermostat end heating element tothe central heating element, that means must be provided to prevent itfrom interfering with the insertion of bread slices into the toastingchamber 67. As illustrated, the bus bar 178 has a substantial portionthereof where it passes the toasting chamber 67 disposed outside theside frame plate 46. To this end, suitable notches 180 and 181 are cutinto the upper edge of the side frame plate 46 to permit the bus bar 178to extend outside the frame plate and to return inside the frame plate,as is very obvious from Figs. 5, 6 and 7 of the drawings. A suitableinsulating strip 182 of mica or the like is disposed between the bus bar178 and the side frame plate 46 to provide the desired electricalinsulation.

The lower end of the heating element 103 is illustrated as beingelectrically interconnected by means of a bus bar 184 with the lower endof the heating element 141a.

One end of the bus bar 1 84 is connected to the terminal belt of theresistor 103, while the other end is suitably connected by means of therivet 149 with the bracket 148, and consequently the lower end of theheating element 141a. A suitable bus bar interconnects the upper ends ofthe heating elements 141a and 14119. The lower end of the heatingelement 14111 is. connected by means of a lead bus bar186 with asuitable terminal stud 187 supported by the subbase 50 adjacent the cordend of the toaster. Preferably the subbase 50 and the insulating base303are arranged to define an insulating chamber generally designated at188 in Fig. 9 of the drawings. This insulating chamber is definedessentially by a cup-shaped member integrally formed with the base 30,which includes an opening 189 to permit access of the appliance cord 170thereto. The top or cover of the insulating recess 188 is defined by aninsulating plate 190 fastened to the underside of the subbafse 50 by themounting stud 187, and an additional mounting stud 191, which is clearlyshown in Figs. 5, 6 and 7 of the drawings. One conductor of theappliance cord 170 is connected to the conductor stud 187 within theinsulated chamber188, and the other conductor of the appliance cord 170is similarly connected to'the conductor stud 191, also within theinsulating chamber 188. To complete the electrical circuit from theconductor stud 191 to the terminal of the switch contact 174, there isprovided a suitable. insulated conductor 192. This insulated conductor 192 preferably extends outside the recess 188 through a suit.- ableopening defined in one of the side walls of the recess 188. Preferablythe conductor 192. is suitably supported along the edge of the base soas not to interfere. with the operative parts of the toaster, since itmust extend from the cord end of the toaster to the thermostat end, asis illustrated in Figs. 3 and 4 of the drawings. For the purpose ofrelieving any strain which might be applied to the appliance cord 170from adversely affecting the connections thereof to the terminal studs187 and 191, a suitable strain relief is provided which is, as illu strated in Fig. 5 pf the drawings, riveted to the subbase 50 and clampedto the appliance cord 170.

2. THEORY UNDERLYING UNIFORM HEATING BY I LINEAR HEAT SOURCES Thistheory is fully described in Koci Patent No. 2,667,- 828, beginning atline 70 of column 23 and extending to line 42 of column 26. Accordingly,this description is not included here, but is incorporated by referencefrom the above-mentioned patent.

3. SHIELDING AGAINST DIRECT RADIATION FROM HEATING- ELEMENTS It will beunderstood that the heating elements described above readily permit ofadequate shielding of the control device to be described hereinafter soas not to be affected by direct radiation from the heating elements ofthe toaster. In other words, with the arrangement described above, it ispossible to permit substantially only radiation from the bread slicesurface being toasted to pass through the opening or Window 168. Tofurther insure that radiant energy from the heating .ele ments 140a and1401: cannot pass through the opening or window 168, the vertical edgesof the opening 168 are provided with flanges 193 which extend from thereflector 156 in the same direction as the heating elements 140a and140b, which is clearly shown in Figs. 7, 17 and 18 of the drawings.These flanges 1 93 cut off any possible direct radiation from theheating elements 140a and 140b, which might have a tendency to passthrough the window 168. In order to prevent radiant energy from thecentral heating element 103 from passing through the opening 168 in theevent that a short bread slice is disposed within the toasting chamber67, there is provided a shield 194 comprising an angle member having asubstantial portion extending horizontally from the top edge of theopening 1.68. This shield 19.4 has a vertical flange suitably riveted asby rivets 194a to the

